High frequency feeder and the like for use with radio aerial systems



May 15, 1934. Q 5 FRANKUN 1,958,991

HIGH FREQUENCY FEEDER AND THE LIKE FOR USE WITH RADIO AERIAL SYSTEMS Filed July 10, 1929 INVENTOR Patented May 15, 1934 HLGH; REQUENOX FEEDER AND THE L KE Eon. sa WIfI -L-B ADIG AERIALYSYSTEMS,

Charles. Samuel'Franklin, Strand, London, Eng' land, as signor to Radio Corporation of America, a corporation; of Del-aware Aar ieatim July; 1.0. 1'929 Se ia1 No... 37-71093- In G eat ritain Jul 8, 1928 4 Claims.

This, inv ntion. relates. tov high. frequency feeders, and the like, for use with radio aerial systerns.

The principal object of the invention is to pro- ;ft vide an improved high frequency feeding arrangement for supplying high frequency energy from a source to an aerial system which is comparatively remote therefrom; for example, for feeding energy from a. source on the ground to an aerial system situated at a considerable height above the ground.

When it is desired to energize an aerial which is located high above the ground from a source of high frequency energy at ground level, it is lit necessary, of course, to provide a feeding wire or wires from said aerial to said source unless said aerial is energized by radiation from a second aerial at or about ground level, as is set forth in the specification No. 259,294.

In one known method of connecting an aerial system to its energizing source, a pair of parallel wires (sometimes called Lecher wires) is employed and, theoretically, so long as the currents in these wires are of equal magnitude and opposite in phase, no loss by radiation from said wires should occur. In practice, however, the balance is very difficult to maintain, it being almost impossible, in many cases, to avoid mutual action between the aerial system and the feeding wires, with the result that currents are induced into the said feeding wires and directional effects desired to be obtained from said aerial system are marred.

In another known method of connecting an aerial system to its energizing source, a single wire is employed. With this arrangement, if the effective resistance of the aerial system at its point of connection to the feeding wire is made equal to the surge impedance of the said wire,

as is set forth in the specification No. 281,762, the energy lost by radiation from said wire need only be small. The losses will, however depend upon the length of the feeding wire and also upon outside conditions in its neighborhood, for example, the presence of conductors.

According to this invention a feeder for supplying high frequency energy from a source to an aerial or aerial system located at a distance therefrom, is constituted by a helical, zigzag or similar wire, the arrangement being such that points of maximum opposite potentials in the travelling wave in said wire are separated spatially by only a fraction of a half wave length.

In one example in accordance with the inven- 55: tion, an aerial system situated a distance of two wave len ths. (measuredin pace.) from its energizing source, is connected thereto by a helical wire, such that the distance in space between points of maximum opposite potentials in the travelling wave in said wire is a quarter of the working wave length. Alternatively, a zigzag Wire may be employed in place of the helical wire. It is found that with these arrangements the energy loss by radiation is about one tenth that which occurs when a simple straight wire two wave lengths long is employed. In such a straight wire, of course, points of maximum opposite potential would be separated spatially by half a wave length.

Feeding systems in accordance with this invention are found to have much reduced radiation losses, while losses due to the neighborhood of conductors are also reduced as compared to those which occur in a simple straight wire.

In order to obtain maximum efficiency and to prevent reflection, the effective resistance of the aerial system at its point of connection to the feeding wire should be made equal to the surge impedance of said wire.

The invention is illustrated in the accompany ing drawing, which shows schematically four arrangements in accordance therewith.

Referring to Figure l, A is an aerial which is fed with high frequency currents from a generator G through a feeder wire F. As will be seen, the feeder wire F is of zigzag form. The straight parts of the wire should be only a fraction of a wave length long, preferably not more than one tenth of a wave length and consecutive points of the wire in which the phase of the travelling wavediifers by 180 are separated spatially from each other by less than a half'wave length-preferably by less than .25 of a wave length.

In the modification shown in Figure 2, the wire F is not truly zigzag but is looped with short rectangular loops all lying on the same side of the general line of direction of the wire.

In the further modification shown in Figure 3, the wire F is formed helically.

Figure 4 shows a feeder arrangement generally similar to the arrangement shown in Figure 1, except that these are two wires F1 F2, each associated with an aerial A1 or A2.

In all the arrangements shown, consecutive points of opposite phase in a wire are separated spatially by less than half a wave length.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that What I claim is:

frequency and a feeder connecting said energy.

producing means to said radiating system, said feeder consisting of a continuous helical conductor, the consecutive turns of which are so spaced that the adjacent points of maximum opposite potential in the current flowing therethrough to said aerial system are separated by less than half a wave length.

3. In combination in a signalling system, an

aerial, a source of alternating current energy, a feed line extending between said aerial and said source, said feed line comprising a single conductor looped at predetermined points along its length which are less than one half wave length apart from one aniotherwith short rectangular loops lying on at least one side of the general line of direction of the wire for preventing radiation from all parts of said feed line.

4. In combination in a signalling system, an aerial, a source of alternating current energy, a feed line extending between said aerial and said source, said feed line comprising a single conductor looped at predetermined points along the length of the conductor with short rectangular loops lying on at least one side of the general line of direction of the wire for preventing radiation from all parts of said feed line, said points being less than one quarter of a wave length apart from one another.

CHARLES SAMUEL FRANKLIN. 

